例谈数列不等式证明的若干放缩技巧

数列问题始终是高考中的一大亮点,在高考中可谓常考常新,尤其是近些年来数列与不等式的融合更成为高考命题者的新宠,而其中对放缩法的把握需要学生有较强的分析和判断能力,因而倍受命题者的青睐.     

磁控溅射制备ZnO薄膜的受激发射特性的研究

用射频磁控反应溅射法在二氧化硅衬底上制备ZnO薄膜。得到了在不同温度下ZnO薄膜的吸收与光致发光。观测到了纵光学波 (LO)声子吸收峰与自由激子吸收峰 ;室温 (30 0K)下 ,PL谱中仅有自由激子发光峰。这些结果证实了ZnO薄膜具有较高的质量。探讨了变温ZnO薄膜的发光特性。研究了ZnO薄膜的受激发射特性。     

EFFECT OF nifA PRODUCT ON SUPPRESSION OF Nif~- PHENOTYPE OF gin MUTATION AND CONSTITUTIVE SYNTHESIS OF NITROGENASE IN Klebsiella pneumoniae

This paper describes the role of nifA product on the ammonia regulation of nitrogen fixation in K. pneumoniae. A plasmid carrying nifA gene under the promoter of tetracycline resistance gene was constructed. When this nifA carrying plasmid was introduced into a glnAG mutant, the Nif~-phenotype of this gln mutant was suppressed. Furthermore, when the plasmid was introduced into the wild type and glnAG mutant, derepression of nitrogenase synthesis in ammonia occurred in both strains and the products of nif genes can be detected by two-dimensional gel electrophoresis in the extracts of these ammonia-grown bacterial cells.The constitutive synthesis of nitrogenase in NH_4~ was also demonstrated in free living nitrogen-fixing bacteria, Enterobacter cloacae, when the bacteria received the plasmid carrying nifA gent from K. pneumoniae.     

末态电子的关联在氢原子(e,2e)反应中的影响(英文)

在共面非对称几何条件下,利用双势公式解析计算了电子碰撞电离氢原子的三重微分截面.对快电子采用平面波近似,跃迁矩阵元可以表示成两个因子乘积的形式,即结构散射因子和出射道两电子的关联因子.在计算过程中对关联因子采取了最简单的近似,当入射能量为150 eV和54.4 eV时,计算结果与实验结果的符合说明对于这些入射能量该关联近似是有效的;而对于入射能量为27.2 eV时,计算结果与实验结果的较大差异说明这种关联近似是无效的.     

Mesons in the Constituent Quark Model

The quark-antiquark （q^-q） spectrum is studied by solving the Schrōdinger equation in the framework of nonrelativistic constituent quark model. An overall good fit to the experimental data of meson is obtained. The interactions between quark and antiquark consist of quadratic colour confinement-exchange, one-gluon-exchange, and Goldstone-boson-exchange potentials.     

白光LED用光转换无机荧光粉

本文综述了近年来白色发光二极管用光转换无机荧光粉的国内外研究进展.分别从能被蓝光LED芯片激发的黄色、绿色与红色荧光粉,和能被近紫外LED芯片激发的蓝色、绿色与红色荧光粉以及单一基质白光荧光粉进行了综述,对性能较好的荧光粉进行了重点推介;对相应的铝酸盐、硅酸盐、氮(氧)化物、钼酸盐等荧光粉的光致发光光谱及其调控原理进行...     

珠算教学中德育和美育的渗透

珠算教学中渗透德育、美育是素质教育的需求,是珠算教学改革中应积极探索的一个领域。爱因斯坦关于教育曾有这样的卓见:“用专业知识教育人是不够的。通过专业教育,他可以成为一种有用的机器,但是不能成为一个和谐发展的人。要使学生对价值有所理解并且产生热烈的感情,那是最基本的。他     

新型二氢吡啶类钙拮抗剂化合物的合成与生物活性

以1,4-二氢-2,6-二甲基-4-(3-硝基苯基)-3,5-吡啶二羧酸单甲酯(1)或双乙烯酮为原料,设计合成了16个未见文献报道的二氢吡啶类钙拮抗剂化合物4a～4l及9a～9d,利用IR,1HNMR,ESI-MS和元素分析对目标化合物的结构进行表征.离体大鼠胸主动脉血管环收缩实验表明,化合物4e,4g～4j对KCl所致的血管环收缩有明显的舒张作用,其生物活性均强于阳性对照苯磺酸左旋氨氯地平.     

Crystal Structure of Catena-poly-[2,2'-bisbenzimidazole Mn(Ⅱ)-μ-Benzene-1,3-dicarboxylato]

The title complex,[(BBI)Mn(BDC)]n 1(BBI = 2,2'-bisbenzimidazole(C14H10N4),BDC=benzene-1,3-dicarboxylate dianion(C8H10O4)),crystallizes in the monoclinic system,space group C2/c,with a=17.822(8),b=16.181(7),c=13.355(6),β=92.112(5)°,V=3848.67(304)3,Z=8,C22H14MnN4O4,Mr=453.31,Dc=1.565 g/cm3,F(000)=1848,μ=0.725 mm-1,S=1.000,the final R=0.0310 and wR=0.0589.1 contains hydrogen bonds and π-π stacking interactions between the neighboring aryl-ring of BBI's,which helps to form a three-dimensional crystal structure.